Liver function tests: Difference between revisions

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==Background==
==Background==
A liver function test is a group of blood tests that, when evaluated as a whole, allow the clinician to determine if there is any damage to the liver, determine if that damage is acute or chronic, and determine if there is hepatobiliary stasis for any reason. The essential components of an LFT includes liver transaminases (AST, ALT), which are surrogates markers of liver health, coagulation studies (PT, PTT, INR), albumin, total protein, lactate dehydrogenase, and liver enzymes GGT and Alkaline Phosphatase which, in conjunction with direct and total bilirubin, are surrogate markers of biliary patency and function.


===Normal Values===
===Normal Values===
*ALT: 7 - 55  U/L
*'''ALT''': 7 - 55  U/L
*AST: 8 - 48 U/L
*'''AST''': 8 - 48 U/L
*Alk Phos: 45 - 115 U/L
*'''Alk Phos''': 45 - 115 U/L
*Albumin: 3.5 to 5.0 g/dL
*'''Albumin''': 3.5 to 5.0 g/dL
*Total protein: 6.3 - 7.9 g/dL
*'''Total protein''': 6.3 - 7.9 g/dL
*Bilirubin: 0.1 - 1.2 mg/dL
*'''Bilirubin''': 0.1 - 1.2 mg/dL
*GGT: 9 - 48 U/L
*'''GGT''': 9 - 48 U/L
*LD: 122 - 222 U/L
*'''LDH''': 122 - 222 U/L
*PT: 11 - 14 seconds
*'''PT''': 11 - 14 seconds
*PTT: 25 - 35 seconds
*'''PTT''': 25 - 35 seconds
*INR: 0.8 - 1.2
*'''INR''': 0.8 - 1.2
 
==Albumin / Total Protein==
 
 
==Bilirubin==
 
 
==Aminotransferases (ALT/AST)==
*Elevation is associated with liver damage
*Elevations in AST >> ALT suggest liver damage from alcoholism (i.e. [[alcoholic hepatitis]])
*Elevations in ALT >> AST suggest liver damage from another etiology (i.e. infectious [[hepatitis]])
 
==Alkaline Phosphatase==
*Predominantly found in the liver, bile ducts, kidney, and bones
*Because of its abundant production in biliary duct tissue, elevation reflects a problem with biliary stasis or obstruction
**Elevation may also occur in patients with increased bone turnover (e.g. 2/2 puberty, osteoporosis, hyperparathyroidism, Paget's disease, etc.)
 
==Gamma-glutamyl Transferase (GGT)==
*Like alkaline phosphatase, also found in abundance in the liver and bile ducts (also spleen, heart, and brain)
*Elevation in conjunction with an elevation in alkaline phosphatase, suggests [[biliary disease|biliary stasis/obstruction]]
 
==Lactate Dehydrogenase (LDH)==
*Found in most body tissues
*Elevation can occur as a result of cellular rupture (different isozymes can specify tissue type involved)
**Cardiac - Demand ischemia, [[myocarditis]]
**Pulmonary - [[pulmonary embolism]]
**GI - hepatitis, small or large bowel obstruction
**Hematologic - [[hemolytic anemia|hemolytic]] process, ineffective erethropoiesis
**Other - pregnancy, cancer, infection, systemic autoimmune disorders


==Interpretation==
==See Also==
==See Also==
==External Links==
*[http://lifeinthefastlane.com/investigations/liver-function-tests/ LITFL LFTs]
*[http://lifeinthefastlane.com/investigations/liver-function-tests/ LITFL LFTs]
*[http://www.mdcalc.com/meld-score-model-for-end-stage-liver-disease-12-and-older/ MDCalc - MELD Score]
*[http://www.mdcalc.com/meld-score-model-for-end-stage-liver-disease-12-and-older/ MDCalc - MELD Score]
==References==
==References==
<references/>
<references/>


[[Category:GI]]
[[Category:GI]]

Latest revision as of 02:05, 21 February 2021

Background

Normal Values

  • ALT: 7 - 55 U/L
  • AST: 8 - 48 U/L
  • Alk Phos: 45 - 115 U/L
  • Albumin: 3.5 to 5.0 g/dL
  • Total protein: 6.3 - 7.9 g/dL
  • Bilirubin: 0.1 - 1.2 mg/dL
  • GGT: 9 - 48 U/L
  • LDH: 122 - 222 U/L
  • PT: 11 - 14 seconds
  • PTT: 25 - 35 seconds
  • INR: 0.8 - 1.2

Albumin / Total Protein

Bilirubin

Aminotransferases (ALT/AST)

  • Elevation is associated with liver damage
  • Elevations in AST >> ALT suggest liver damage from alcoholism (i.e. alcoholic hepatitis)
  • Elevations in ALT >> AST suggest liver damage from another etiology (i.e. infectious hepatitis)

Alkaline Phosphatase

  • Predominantly found in the liver, bile ducts, kidney, and bones
  • Because of its abundant production in biliary duct tissue, elevation reflects a problem with biliary stasis or obstruction
    • Elevation may also occur in patients with increased bone turnover (e.g. 2/2 puberty, osteoporosis, hyperparathyroidism, Paget's disease, etc.)

Gamma-glutamyl Transferase (GGT)

  • Like alkaline phosphatase, also found in abundance in the liver and bile ducts (also spleen, heart, and brain)
  • Elevation in conjunction with an elevation in alkaline phosphatase, suggests biliary stasis/obstruction

Lactate Dehydrogenase (LDH)

  • Found in most body tissues
  • Elevation can occur as a result of cellular rupture (different isozymes can specify tissue type involved)
    • Cardiac - Demand ischemia, myocarditis
    • Pulmonary - pulmonary embolism
    • GI - hepatitis, small or large bowel obstruction
    • Hematologic - hemolytic process, ineffective erethropoiesis
    • Other - pregnancy, cancer, infection, systemic autoimmune disorders

See Also

External Links

References